Anhydrous ammonia is commonly used as a fertilizer for growing row crops. A wide toolbar with a plurality of injector knives that extend into the ground along the multiple rows is pulled behind a tractor. The injector knives are connected to tubing which extends to one or more control sections where a flow stream of anhydrous ammonia is divided into separate streams for directing to respective ones of the injector knives. A flow hose extends from the one or more control sections to a nurse tank which is also pulled behind the tractor. The nurse tank provides a supply of liquid anhydrous ammonia. A flow nozzle and a flow nozzle coupling are mounted to the terminal end of the hose for connecting to a fitting which is mounted to the nurse tank and provides a flow connector for passing anhydrous ammonia form the nurse tank into the flow hose. The flow nozzle coupling typically has acme threads for connecting to the fitting, and the nozzle coupling is often hand tightened when secured to the fitting for ease of connecting the nurse tank to the tractor and ease of releasing the flow hose from the tractor. Vibration encountered when the tractor, toolbar and nurse tank are moving across a field on occasion causes the nozzle coupling to loosen from the fitting, causing unwanted release of anhydrous ammonia.